Dynamically Corrected Bethe-Salpeter Equation Solver for Self-consistent $GW$ Reference on the Matsubara Frequency Axis

TL;DR

This paper introduces a new BSE solver based on self-consistent GW on the Matsubara axis, incorporating dynamical screening effects via a plasmon-pole model, leading to accurate excitation energies.

Contribution

The work develops a dynamically corrected BSE@scGW method that improves excitation energy predictions by combining a self-consistent GW reference with a simple dynamical screening model.

Findings

Achieves excitation energies close to high-level benchmarks.

Reduces sensitivity to initial mean-field references.

Effectively incorporates dynamical screening effects.

Abstract

We present a Bethe-Salpeter equation (BSE) solver based on a self-consistent $GW$ reference evaluated on the Matsubara frequency axis, referred to as BSE@sc$GW$. The self-consistent $GW$ starting point provides a robust quasiparticle description and reduces sensitivity to the initial mean-field reference compared to one-shot $GW$-based approaches. We further introduce a dynamical correction to the static Casida formulation via a plasmon-pole model. This scheme incorporates simple dynamical screening effects while retaining the efficiency of an effective eigenvalue problem. The resulting dynamically corrected BSE@sc$GW$ yields excitation energies in close agreement with high-level wavefunction-based benchmarks for both singlet and triplet excitations of small molecules. Overall, the accuracy of the dynamic BSE@sc$GW$ approach arises from the combination of a well-converged single-particle reference and the inclusion of frequency-dependent screening effects.